Golf is an increasingly popular outdoor game that may be played by persons of all ages using long-shafted clubs and a small ball on a large, grassy outdoor expanse called a course. Each golfer tries to hit the ball from the starting area called a tee into a small, sunken cup generally located on a green that is between 100 to 600 yards from the tee with as few strokes as possible. A typical golf course consists of 9 or 18 playing areas called holes, each of which is assigned a value called par, which is the average number of strokes an expert player would require to play the hole. For strokes or shots used to reach the green, the ball is typically hit with a driver club or iron club into the air. Upon reaching the green, the ball is typically hit with a putter club so that it travels entirely by rolling on the ground.
Putts and short chips (a short and low approach shot where the ball makes a shallow flight and then rolls out on the green) are ideally played without much movement of the body, but most other golf shots are played using variants of a full golf swing. The full golf swing is notoriously difficult to learn, and involves an unnatural, highly complex rotation of the body, the objective of which is to accelerate the club head so as to achieve maximum speed at the bottom of the stroke as the ball is struck. It is not uncommon for beginners to spend several months practicing the swing basics before playing their first ball on a course. It is generally considered impossible to acquire a stable and successful swing without professional instruction and even highly skilled golfers may continue to take golf lessons for many years. For a right-handed golfer, the full swing consists of a backswing to the right, a downswing to the left (in which the ball is hit), and a follow through. At address, the player stands with the left shoulder and hip pointing in the intended direction of ball flight, with the ball before the feet. The club is held with both hands (right below left for right-handed players), the clubhead resting on the ground behind the ball, hips and knees somewhat flexed, and the arms hanging from the shoulders. The backswing is a rotation to the right, consisting of a shifting of the player's body weight to the right side, a turning of the pelvis and shoulders, lifting of the arms and flexing of the elbows and wrists. At the end of the backswing the hands are above the right shoulder, with the club pointing more or less in the intended direction of ball flight. The downswing is roughly a backswing reversed. After the ball is hit, the follow-through stage consists of a continued rotation to the left. At the end of the swing, the weight has shifted almost entirely to the left foot, the body is fully turned to the left and the hands are above the left shoulder with the club hanging down over the players' back. Relatively few golfers play left-handed (i.e., swing back to the left and forward to the right), with even players who are strongly left-handed in their daily life preferring the right-handed golf swing. (Wikipedia, article about golf, updated Aug. 1, 2006)
Given the difficulty of mastering the full golf swing, it is not surprising that a plethora of golf swing trainers have been developed over the years. U.S. Pat. No. 1,471,794 to Charles Leven discloses a practice golf club having a head connected via a toothed shaft to a coil spring. As the head is driven away from the handle when subjected to centripetal force, a spring-loaded pawl locks the toothed shaft in its most extended position, thereby providing an indication of the rotational speed of the club. U.S. Pat. No. 1,662,712 to Carl F. Mensing discloses a golf club having a flexible, whip-like shaft which compels the user to swing smoothly and thereby improve his swing. U.S. Pat. No. 1,930,342 to Mack C. Graham discloses a Golf Practice Club which combines a conventional club shaft and handle with an adjustable weight that is connected to the bottom end of the shaft with a chain, a wire or other flexible element. The loosely-coupled weight will jerk the shaft if the downswing is begun prematurely. U.S. Pat. No. 3,428,325 to Garland P. Atkinson discloses a Golf Swing Training Device having a rigid handle and a padded weight coupled to the bottom end of the handle with a flexible elastic cord. The training device assists in the development of a proper swing by allowing a right-handed user to feel the padded weight strike him in the left chest or shoulder during the backswing and in the right chest or shoulder at the end of the followthrough. In addition, proper timing of the swing is encouraged if the weight smoothly follows the arc of the shaft. U.S. Pat. No. 4,343,473 to Paul D. Laursen discloses a Golf Swing Trainer having a rigid hand grip connected at the bottom end thereof to a shaft formed of a limp, flexible material such as nylon rope. The free end of the shaft is unravelled to form a soft tassel. The swing trainer encourages the user to use his entire body during the downswing so that the flexible shaft can be pulled through the ball impact region. U.S. Pat. No. 4,982,963 to Jerry J. Fazio, et al. discloses a Golf Club Swing Training Device having a laterally curvable shaft made of an elastomeric material such as neoprene rubber, with a head member made of resilient material attached to the end of the shaft. The device is designed to give the user an improved feel for the swing, and retains the advantage that the device cannot be swung property unless all the various aspects of the swinging of the golf club are properly coordinated. U.S. Pat. No. 5,316,306 to Douglas R. Cody discloses a Golf Swing Training Device having a rigid had grip connected to one end of a flexible tubular shaft.